This invention relates to a communication technology for transmitting error correction coded information effectively through a communication system which has not been designed to process the error correction coded information with minimized modification thereof.
With a conventional communication system which has not been designed to transmit the error correction coded information, a transmission side serves to add error-detecting information to each transmission frame. An addressed reception side receives the transmission frame as FIG. 9 shows (step 605), and inspects whether or not the received frame has an error (step 600) by using the error-detecting information added to the transmission frame. If it is determined that an error exists in the received frame (step 601), the frame is abandoned (step 602).
While if it is determined that no error exists in the received frame, inspection is executed for each channel type (step 603), and the process further proceeds to the next step (step 604), where it is determined whether or not communication has been completed (step 606). If the communication has been completed, the line is disconnected. If it is determined that the communication has not been completed, the process returns to the step 605.
In order to make up for the abandoned frame, re-transmission of the same frame is required through, for example, an ARQ system (See Vijay K. Bhargava, David Ahccoun, Robert Matyas, and Peter P. Nuspl, "Digital Communications by Satellite", Willey & Sons, Inc., 1983).
With the above system, deterioration of the channel quality may increase the error rate in the frame, and demand frequent frame re-transmission, thus degrading transmission efficiency. In order to prevent the above described degradation of the transmission efficiency, an art for error correction coding has been disclosed. This art is used to correct the error correctable within a capacity of the error correction code, and to keep the transmission efficiency from degrading.
However such system is required to be designed on an assumption that the information which has been previously error correction coded is transmitted so as to improve transmission efficiency through the error correction coding technology. The system which has not been designed to transmit the error correction coded information as described above is so constructed to abandon the received frame if an error is found from the error-detecting information added to the transmission frame. Accordingly although the error correction coded information is transmitted, its function cannot work well, thus failing to overcome degradation of the transmission efficiency.